Study approach and model framework. Left panels represent observed data and right panels make reference to models. The modelling framework, describing intra-herd and inter-herd C. burnetii dynamics and the different transmission routes, is sketched in the top right panel: herd A is an initially prevalent herd, herd B is an initially susceptible herd further infected by cattle trade, and herd C is an initially susceptible herd further infected by airborne transmission. Inter-herd transmission is due to airborne dispersion (dashed arrows) and trade of cows (solid arrows). Intra-herd infection dynamics (detailed in Figure 2) is influenced by the bacteria shed by infected cows (red) contributing to infect susceptible cows (blue). Shapes representing cows correspond to the shape of their original herd. The initial conditions of the model are based on the observed regional prevalence in the Finistère department in 2012 (top left panel; the inset locates the Finistère department in France). Model predictions of newly infected herds in Finistère department for 2013 (bottom right panel) are compared with the observed newly infected herds in 2013 (bottom left panel) using receiver operating characteristics (ROC) analysis.